Solid-state imaging device, signal processing method therefor, and electronic apparatus for enabling sensitivity correction

ABSTRACT

The present disclosure relates to a solid-state imaging device, a signal processing method therefor, and an electronic apparatus enabling sensitivity correction in which a sensitivity difference between solid-state imaging devices is suppressed. 
     The solid-state imaging device includes a pixel unit in which one microlens is formed for a plurality of pixels in a manner such that a boundary of the microlens coincides with boundaries of the pixels. The correction circuit corrects a sensitivity difference between the pixels inside the pixel unit based on a correction coefficient. The present disclosure is applicable to, for example, a solid-state imaging device and the like.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 16/589,373, filed Oct. 1, 2019, which is acontinuation of and claims priority to U.S. patent application Ser. No.15/873,580, filed Jan. 17, 2018, now U.S. Pat. No. 10,542,229, which isa continuation of and claims priority to U.S. patent application Ser.No. 15/029,763, filed Apr. 15, 2016, now U.S. Pat. No. 9,918,031, whichis a national stage application under 35 U.S.C. 371 and claims thebenefit of PCT Application No. PCT/JP2015/073463 having an internationalfiling date of Aug. 21, 2015, which designated the United States, whichPCT application claimed the benefit of Japanese Patent Application No.2014-177171 filed Sep. 1, 2014, the disclosures of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a solid-state imaging device, a signalprocessing method therefor, and an electronic apparatus, andparticularly relates to a solid-state imaging device, a signalprocessing method therefor, and an electronic apparatus enablingsensitivity correction in which a sensitivity difference betweensolid-state imaging devices is suppressed.

BACKGROUND ART

In a solid-state imaging device such as a CMOS image sensor, there is adisclosed example in which a phase difference in an object image isdetected by dividing a photodiode that partly shields light of amicrolens or receives a light flux collected by a microlens, and thedetection result is used for focus detection and the like (PatentDocuments 1 and 2, for example).

In this kind of the solid-state imaging device having a function ofphase difference detection, positional shift relative to the photodiodetends to occur in the microlens and a shielding portion due to amanufacture process thereof, and such positional shift may cause asensitivity difference between a pixel pair in which a phase differenceis detected. Since an output difference between a pixel pair is used indetecting a phase difference, the sensitivity difference caused by anerror (positional shift) during manufacture may become a factor todegrade accuracy of the phase difference. Since such a manufacture erroris varied by a lot and the like during production, for example, a levelof the sensitivity difference and a direction of magnitude thereof aredifferent between solid-state imaging devices.

Considering this, there is a disclosed solid-state imaging device thatcorrects a sensitivity difference caused by a manufacture error (PatentDocument 3, for example). According to an embodiment of Patent Document3, in a pixel pair where a sensitivity difference is caused, outputadjustment is performed for a pixel having higher output by multiplyinga pixel having lower output by a correction coefficient.

CITATION LIST Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-250931

Patent Document 2: Japanese Patent Application Laid-Open No. 2005-303409

Patent Document 3: Japanese Patent Application Laid-Open No. 2010-237401

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, according to a correction method disclosed in Patent Document3, a sensitivity difference between a pixel pair is resolved bycorrection, but there is no reference for a value to be corrected by acorrection coefficient. Therefore, a pixel output value after correctionmay be varied by a degree of variation of solid-state imaging devices.For example, even when the solid-state imaging devices having the samemodel number are used, values output from the solid-state imagingdevices under a same light amount become different in the respectivesolid-state imaging devices. As a result, detection accuracy of phasedifference may be varied by each chip, and brightness of an image may bevaried by each chip when pixel output of the phase difference isutilized for preview and the like at the time of focusing.

The present disclosure is made in view of the above-described situation,and directed to enabling sensitivity correction in which a sensitivitydifference between solid-state imaging devices is suppressed.

Solutions to Problems

A solid-state imaging device according to a first aspect of the presentdisclosure, includes: a pixel unit in which one microlens is formed fora plurality of pixels in a manner such that a boundary of the microlenscoincides with boundaries of the pixels; and a correction circuitadapted to correct a sensitivity difference between pixels inside thepixel unit based on a correction coefficient.

In a signal processing method for a solid-state imaging device accordingto a second aspect of the present disclosure, the solid-state imagingdevice includes a pixel unit in which one microlens is formed for aplurality of pixels in a manner such that a boundary of the microlenscoincides with boundaries of the pixels, and a correction circuit of thesolid-state imaging device corrects a sensitivity difference betweenpixels inside the pixel unit based on a correction coefficient.

An electronic apparatus according to a third aspect of the presentdisclosure is provided with a solid-state imaging device that includes:a pixel unit in which one microlens is formed for a plurality of pixelsin a manner such that a boundary of the microlens coincides withboundaries of the pixels; and a correction circuit adapted to correct asensitivity difference between pixels inside the pixel unit based on acorrection coefficient.

According to the first to third aspects of the present disclosure, theabove-described one microlens is formed for the plurality of pixels inthe pixel unit of the solid-state imaging device in a manner such thatthe boundary of the microlens coincides with the boundaries of thepixels. In the correction circuit, the sensitivity difference betweenthe pixels inside the pixel unit is corrected based on the correctioncoefficient.

The solid-state imaging device and the electronic apparatus may beindependent devices or modules incorporated in another device.

Effects of the Invention

According to first to third aspects of the present disclosure, it ispossible to perform sensitivity correction in which a sensitivitydifference between solid-state imaging devices is suppressed.

Note that the effect recited herein is not necessarily limited theretoand may be any one of those recited in the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a first embodiment of asolid-state imaging device according to the present disclosure.

FIG. 2 is a diagram illustrating a cross-sectional structure of pixels.

FIG. 3 is an explanatory diagram for a pixel unit.

FIG. 4 is an explanatory diagram for the pixel unit.

FIG. 5 is a diagram illustrating an exemplary circuit configuration of apixel.

FIG. 6 is a diagram illustrating an exemplary circuit configuration ofpixels in the case of having a pixel sharing structure.

FIG. 7 is an explanatory diagram for a sensitivity difference caused bypositional shift of a microlens.

FIG. 8 is an explanatory diagram for the sensitivity difference causedby positional shift of the microlens.

FIG. 9 is an explanatory diagram for sensitivity difference correctionprocessing.

FIG. 10 is an explanatory flowchart for the correction coefficientcalculation processing.

FIG. 11 is an explanatory flowchart for correction coefficientcalculation processing using FD adding.

FIG. 12 is a diagram illustrating an exemplary correction table.

FIG. 13 is an explanatory flowchart for sensitivity differencecorrection processing.

FIG. 14 is an explanatory diagram for the sensitivity differencecorrection processing per wavelength.

FIG. 15 is an explanatory diagram for the sensitivity differencecorrection processing per wavelength.

FIG. 16 is an explanatory diagram for the sensitivity differencecorrection processing for a white pixel.

FIG. 17 is an explanatory diagram for the sensitivity differencecorrection processing for the white pixel.

FIG. 18 is a diagram illustrating a modified example of arrangement ofthe pixel unit.

FIG. 19 is a diagram illustrating a first exemplary structure in whichthe pixel unit is formed of two pixels.

FIG. 20 is a diagram illustrating a second exemplary structure in whichthe pixel unit is formed of two pixels.

FIG. 21 is an explanatory diagram for correction coefficient calculationprocessing in the case where the pixel unit is formed of the two pixels.

FIG. 22 is an explanatory diagram for exemplary substrate configurationsof the solid-state imaging device.

FIG. 23 is a block diagram illustrating a second embodiment of asolid-state imaging device according to the present disclosure.

FIG. 24 is a block diagram illustrating a third embodiment of asolid-state imaging device according to the present disclosure.

FIG. 25 is a block diagram illustrating an exemplary configuration of animaging device as an electronic apparatus according to an embodiment ofthe present disclosure.

MODE FOR CARRYING OUT THE INVENTION

A mode for carrying out the present disclosure (hereinafter referred toas embodiment) will be described below. Note that the description willbe provided in the following order.

1. First Embodiment (exemplary structure of a solid-state imaging deviceincluding a correction circuit and a memory)

2. Second Embodiment (exemplary structure of a solid-state imagingdevice including a correction circuit)

3. Third Embodiment (exemplary structure of a camera module including acorrection circuit and a memory)

4. Exemplary Application to Electronic Apparatus

1. First Embodiment Exemplary Schematic Structure of Solid-State ImagingDevice

FIG. 1 is a block diagram illustrating a schematic configuration of asolid-state imaging device according to the present disclosure.

A solid-state imaging device 1 in FIG. 1 includes: a pixel array unit 3in which a plurality of pixels 2 is arrayed in a matrix (FIG. 2 ); andperipheral circuit portions in the periphery thereof. In the peripheralcircuit portions, a vertical drive unit 4, an AD conversion unit 5, ahorizontal drive unit 6, a timing control unit 7, a signal processingcircuit 8, an output circuit 9, and so on are included.

The pixel 2 is formed of a photodiode as a photoelectric conversion unitand a plurality of pixel transistors. The plurality of pixel transistorscorresponds to, for example, MOS transistors such as a transfertransistor, an amplification transistor, a selection transistor, and areset transistor. An exemplary circuit configuration of the pixel 2 willbe described later with reference to FIGS. 5 and 6 .

The vertical drive unit 4 is formed of, for example, a shift register,and drives the pixels 2 in units of row by supplying drive pulses to therespective pixels 2 via pixel drive wiring (not illustrated). Morespecifically, the vertical drive unit 4 sequentially and selectivelyscans each of the pixels 2 of the pixel array unit 3 in units of row ina vertical direction, and supplies the AD conversion unit 5 with a pixelsignal based on signal charge generated in accordance with an incidentlight amount in the photodiode of each of the pixels 2 via a verticalsignal line provided in common in units of column (not illustrated).

The AD conversion unit 5 applies, to the pixel signal output from eachof the pixels 2 in one of the rows of the pixel array unit 3, ADconversion processing and correlated double sampling (CDS) processing inorder to remove fixed pattern noise unique to the pixel.

The horizontal drive unit 6 is formed of, for example, a shift registerand sequentially outputs horizontal scanning pulses, thereby outputting,to the signal processing circuit 8, a (digital) pixel signal of each ofthe pixels in a predetermined row that has been subjected to the ADconversion and held in the AD conversion unit 5.

The timing control unit 7 receives an input clock and data to command anoperation mode and the like, and further outputs data such as internalinformation of the solid-state imaging device 1. More specifically, thetiming control unit 7 generates a clock signal and a control signal tobe reference of operation in the vertical drive unit 4, AD conversionunit 5, and horizontal drive unit 6 based on a vertical synchronizationsignal, a horizontal synchronization signal, and a master clock.Further, the timing control unit 7 outputs the generated clock signaland control signal to the vertical drive unit 4, AD conversion unit 5,horizontal drive unit 6, and so on.

The signal processing circuit 8 includes at least a correction circuit11 and a memory 12, executes sensitivity difference correctionprocessing to correct a sensitivity difference between the respectivepixels, and outputs a pixel signal subject to this processing to theoutput circuit 9.

More specifically, the correction circuit 11 executes the sensitivitydifference correction processing to correct the sensitivity differencebetween the respective pixels based on a correction coefficient storedin the memory 12. Further, the correction circuit 11 also executescorrection coefficient calculation processing to calculate a correctioncoefficient needed in executing the sensitivity difference correctionprocessing, and to make the memory 12 store the calculated correctioncoefficient.

The memory 12 stores the correction coefficient calculated in thecorrection coefficient calculation processing executed by the correctioncircuit 11, and supplies the same to the correction circuit 11 whenneeded.

The output circuit 9 executes buffering for the signals sequentiallyoutput from the signal processing circuit 8, and outputs the signals toan external circuit such as an image signal processor (ISP) in afollowing stage.

The solid-state imaging device 1 thus configured is, for example, a CMOSimage sensor of a so-called column AD system in which the CDS processingand the AD conversion processing are performed in units of pixel row.

Cross-Sectional Structure of Pixels

FIG. 2 is a diagram illustrating a cross-sectional structure of thepixels 2 arranged in a matrix inside the pixel array unit 3 of FIG. 1 .

In each of the pixels 2 in the pixel array unit 3, for example, aphotodiode PD is formed per pixel by forming an n-type (secondconductive type) semiconductor region 22 per pixel on a semiconductorsubstrate (silicon substrate) 20 formed with a p-type (first conductivetype) semiconductor region 21. Meanwhile, in FIG. 2 , the semiconductorregion 21 is partitioned per pixel for convenience sake, but note thatsuch boundaries do not exist actually.

A front surface side of the semiconductor substrate 20 (lower side inFIG. 2 ) is formed with: a plurality of pixel transistors adapted toread electric charge accumulated in the photodiode PD; and a multi-layerwiring layer formed of a plurality of wiring layers and an interlayerdielectric film (all not illustrated).

On the other hand, a back surface side of the semiconductor substrate 20(upper side in FIG. 2 ) is formed with an oxide film 23 such as a TEOSfilm interposing a reflection prevention film formed of, for example, asilicon oxide film or the like (not illustrated).

A light shielding film 24 is formed at a two-pixel interval at a pixelboundary portion on the back surface side of the semiconductor substrate20. The light shielding film 24 may be a light-shielding material, andpreferably, has a high light-shielding property and is made of thematerial that can be precisely processed by microfabrication such asetching. The light shielding film 24 may be formed of a metallic filmsuch as tungsten (W), aluminum (Al), copper (Cu), titanium (Ti),molybdenum (Mo), and nickel (Ni).

A color filter 25 is formed on an upper surface of the oxide film 23.The color filter 25 is any one of red, green, and blue, and transmitslight of only a predetermined color (wavelength) to the photodiode PD.The color filter 25 is formed by, for example, performing spin-coatingof photopolymer containing a coloring matter such as a pigment or dye.

A microlens (on-chip lens) 26 is formed on the color filter 25. Themicrolens 26 is formed of, for example, a resin-based material such as astyrene-based resin, an acrylic-based resin, a styrene/acrylcopolymer-based resin, or a siloxane-based resin.

As illustrated in FIG. 3 , one microlens 26 is formed for four pixelshaving a 2×2 structure in which two pixels are arrayed respectively in ahorizontal direction and a vertical direction. The microlens 26 isarranged in a manner such that a boundary of the microlens 26 coincideswith at least a boundary between the pixels 2.

Further, as for a color array of the color filter 25 also, the colorfilters 25 of red, green, or blue are formed such that the photodiodesPD of the four pixels having the 2×2 structure and sharing one microlens26 receive light having the same wavelength and such that a Bayer arrayis formed in the unit of four pixels having the 2×2 structure.

In the following description, a sharing unit of the four pixels havingthe 2×2 structure in which one microlens 26 is shared will be referredto as a pixel unit 31.

Further, in the following description, as illustrated in FIG. 4 , anupper-left pixel 2 will be referred to as a pixel A, an upper-rightpixel 2 as a pixel B, a lower-left pixel 2 as a pixel C, and alower-right pixel 2 as a pixel D in the four pixels having the 2×2structure and forming the pixel unit 31. Further, a pixel 2 formed witha red color filter 25 will be referred to as a red pixel, a pixel 2formed with a green color filter 25 as a green pixel, and a pixel 2formed with a blue color filter 25 as a blue pixel as well.

The pixels 2 are formed as described above, and the solid-state imagingdevice 1 is a back-illumination type CMOS solid-state imaging device inwhich light is incident from the back surface side that is an oppositeside of the front surface side of the semiconductor substrate 20 wherethe pixel transistors are formed.

As illustrated in FIGS. 2 and 3 , in the case where one microlens 26 isshared by the plurality of pixels 2, for example, deviation may occurbetween images formed from the two photodiodes PD because formedpositions of the photodiodes PD relative to the microlens 26 aredifferent between the photodiode PD of the pixel A and the photodiode PDof the pixel B. Based on this image deviation, a defocus amount iscalculated by calculating a phase deviation amount, and auto-focus canbe achieved by adjusting (moving) a photographing lens.

Therefore, in the case where one microlens 26 is shared by the pluralityof pixels 2 as illustrated in FIG. 2 , auto-focus can be achieved bydetecting a phase difference, using a pixel signal of each of the pixelssharing one microlens 26.

Exemplary Circuit Configuration of Pixel

FIG. 5 is a diagram illustrating an exemplary circuit configuration ofthe pixel 2.

The pixel 2 includes the photodiode PD as a photoelectric conversionunit, a transfer transistor 41, a floating diffusion (FD) 42, a resettransistor 43, an amplification transistor 44, and a selectiontransistor 45.

The photodiode PD generates and accumulates electric charge (signalcharge) according to a received light amount. The photodiode PD has ananode terminal grounded, and further a cathode terminal connected to theFD 42 via the transfer transistor 41.

The transfer transistor 41 reads electric charge generated at thephotodiode PD and transfers the same to the FD 42 when the transfertransistor is turned on by a transfer signal TG.

The FD 42 holds the electric charge read from the photodiode PD. Whenthe reset transistor 43 is turned on by a reset signal RST, the electriccharge accumulated in the FD 42 is discharged to a drain (constantvoltage source Vdd), thereby resetting potential of the FD 42.

The amplification transistor 44 outputs a pixel signal according to thepotential of the FD 42. More specifically, the amplification transistor44 constitutes a source follower circuit with a load MOS (notillustrated) as a constant current source connected via a verticalsignal line 46. A pixel signal indicating a level according to theelectric charge accumulated in the FD 42 is output to the AD conversionunit 5 from the amplification transistor 44 via the selection transistor45.

The selection transistor 45 is turned on when the pixel 2 is selected bya selection signal SEL, and outputs the pixel signal generated in thepixel 2 to the AD conversion unit 5 via the vertical signal line 46.Respective signal lines whereby the transfer signal TG, selection signalSEL, and reset signal RST are transmitted are connected to the verticaldrive unit 4 in FIG. 1 .

The pixel 2 can be configured as described above, but not limited tothis configuration, and other configurations can be also adopted.

Exemplary Circuit Configuration of Pixel Sharing Structure

For example, the pixels 2 have a pixel sharing structure in which the FD42, reset transistor 43, amplification transistor 44, and selectiontransistor 45 are shared by four pixels 2 constituting the pixel unit31.

FIG. 6 is a diagram illustrating an exemplary circuit configuration ofthe pixel unit 31 in the case of having the pixel sharing structure.

In the pixel sharing structure, each of the pixels A to D constitutingthe pixel unit 31 individually includes only the photodiode PD and thetransfer transistor 41.

More specifically, the pixel A includes a photodiode PD_(A) and atransfer transistor 41 _(A), the pixel B includes a photodiode PD_(B)and a transfer transistor 41 _(B), the pixel C includes a photodiodePD_(C) and a transfer transistor 41 _(C), and the pixel D includes aphotodiode PD_(D) and a transfer transistor 41 _(D).

Further, the FD 42, reset transistor 43, amplification transistor 44,and selection transistor 45 are respectively used in common by the fourpixels constituting the sharing unit.

In the case where the transfer transistors 41 _(A) to 41 _(D) of thepixels A to D are separately turned on and electric charge accumulatedin the respective photodiodes PD_(A) to PD_(D) are sequentiallytransmitted to the FD 42, a pixel signal per pixel is output to the ADconversion unit 5. In the present embodiment, this imaging mode will bereferred to as an independent pixel mode.

On the other hands, in the case where the transfer transistors 41 _(A)to 41 _(D) of the pixels A to D are simultaneously turned on andelectric charge accumulated in the respective photodiodes PD_(A) toPD_(D) are simultaneously transmitted to the FD 42, the FD 42 functionsas an adding unit, and an added signal obtained by adding the pixelsignals of the four pixels inside the pixel unit 31 is output to the ADconversion unit 5. In the present embodiment, this imaging mode will bereferred to as a pixel adding mode.

Therefore, in accordance with a drive signal from the vertical driveunit 4, the plurality of pixels 2 inside the pixel unit 31 can output apixel signal per pixel and also can simultaneously output the pixelsignals of the plurality of pixels 2 inside the pixel unit 31.

Description for Sensitivity Difference Caused by Positional Shift ofMicrolens

Meanwhile, according to the example illustrated in FIG. 3 , the exampleof disposing the microlens 26 such that a center of the microlens 26coincides with a center of the pixel unit 31 has been provided, but inan actual manufacturing process, the position of the microlens 26 may beslightly shifted from the center of the pixel unit 31.

In the case where the position of the microlens 26 is shifted from thecenter of the pixel unit 31, a sensitivity difference is caused betweenthe pixels inside the pixel unit 31.

The sensitivity difference caused by positional shift of the microlens26 will be described with reference to FIGS. 7 and 8 .

FIG. 7 is an explanatory diagram for light intensity of incident lightin the case of no positional shift of a microlens 26.

Light (light flux) from an object is collected at the microlens 26disposed at an upper portion of the pixel unit 31 at the time offocusing, and reaches the photodiode PD of each of the pixels 2 insidethe pixel unit 31.

In a diagram A of FIG. 7 , an inner portion of a dashed-line circleshown inside the pixel unit 31 indicates a region having the lightintensity of a predetermined value or more inside the pixel unit 31 byreceiving incident object light collected at the microlens 26.

In the case of no positional shift of the microlens 26, as illustratedin the diagram A of FIG. 7 , the light intensity of the object lightcollected at the microlens 26 is uniformly distributed to each of thepixels 2. Further, as illustrated in a diagram B of FIG. 7 , the pixelsignals (output values) output from the respective pixels 2 of thepixels A to D become same.

FIG. 8 is an explanatory diagram for the light intensity of incidentlight in the event of positional shift of a microlens 26.

In the event of positional shift of the microlens 26, the center of thedashed-line circle indicating the region having the light intensity ofthe predetermined value or more is deviated from the center of the pixelunit 31 as illustrated in a diagram A of FIG. 8 , and the region insidethe dashed-line circle in each of the pixels is different in each pixel.As a result, as illustrated in a diagram B of FIG. 8 , the pixel signals(output values) output from the respective pixels 2 of the pixels A to Dare different in the respective pixels.

As described above, in the case where the position of the microlens 26is shifted from the center of the pixel unit 31, a sensitivitydifference is caused between the pixels inside the pixel unit 31.

The signal processing circuit 8 performs the sensitivity differencecorrection processing to correct the sensitivity difference between thepixels inside the pixel unit 31 caused by a manufacture error such aspositional shift of the microlens 26 as described above.

Note that only the positional shift of the microlens 26 has beendescribed as the manufacture error for easy understanding, but thereason causing the sensitivity difference is not limited to thepositional shift of the microlens 26. The signal processing circuit 8can correct, by the sensitivity difference correction processing, asensitivity difference between the pixels inside the pixel unit 31caused by reasons including manufacture errors of various kinds of filmsother than the positional shift of the microlens 26.

Sensitivity Difference Correction Processing

The sensitivity difference correction processing executed by the signalprocessing circuit 8 will be described.

In the sensitivity difference correction processing, attention is paidto a point that a position of the dashed-line circle indicating theregion having the light intensity of the predetermined value or more isfitted inside the pixel unit 31 as illustrated in the diagram A of FIG.8 even when a manufacture error occurs in the solid-state imaging device1. In other words, according to the sensitivity difference correctionprocessing, there is a precondition that a manufacture error which maycause the dashed-line circle indicating the region having the lightintensity of the predetermined value or more to come out of the area ofthe pixel unit 31 does not occur.

Therefore, in the case of observing a total amount of the incident lightper the pixel unit 31, there is no difference between the case of havingno manufacture error and the case of having a manufacture error. Inother words, there is no difference in the total amount of the incidentlight between the pixel unit 31 in the diagram A of FIG. 7 and the pixelunit 31 in the diagram A of FIG. 8 , and there may be a mere change in adistribution ratio of the light intensity to the respective pixelsinside the pixel unit 31. The same happens even in the case where apositional shift direction is varied by each solid-state imaging device1 because of a different production lot.

Therefore, as illustrated in FIG. 9 , a pixel average value SigAve ofthe pixel signals of the four pixels inside the pixel unit 31 becomessame as a pixel signal (pixel output value) of each of pixels in anideal state of having no manufacture error.

Therefore, as the correction coefficient calculation processing, thecorrection circuit 11 of the signal processing circuit 8 calculates thepixel average value SigAve of the pixel signals of the four pixelsinside the pixel unit 31, and calculates a ratio between the pixelaverage value SigAve and the pixel output value of each of the pixelsinside the pixel unit 31 as a correction coefficient.

More specifically, the correction circuit 11 calculates a correctioncoefficient a of the pixel A inside the pixel unit 31 based on a ratioSigAve/Sig1 (a =SigAve/Sig1) between the pixel average value SigAve anda pixel output value Sig1 of the pixel A. Further, the correctioncircuit 11 calculates a correction coefficient b of the pixel B insidethe pixel unit 31 based on a ratio SigAve/Sig2 (b=SigAve/Sig2) betweenthe pixel average value SigAve and a pixel output value Sig2 of thepixel B. The correction circuit 11 also calculates correctioncoefficients c and d of the pixels C and D in the same manner based on:c=SigAve/Sig3 and d=SigAve/Sig4. The calculated correction coefficientsa to d in each pixel unit 31 are stored in the memory 12.

Flowchart of Correction Coefficient Calculation Processing

The correction coefficient calculation processing to calculate acorrection coefficient will be described with reference to a flowchartin FIG. 10 . The processing is executed in, for example, an inspectionprocess after manufacturing the solid-state imaging device 1.

First, in Step S1, imaging is performed based on the independent pixelmode in a state that the entire pixel array unit 3 of the solid-stateimaging device 1 is irradiated with uniform light, and the correctioncircuit 11 of the solid-state imaging device 1 obtains and stores pixelsignals of all of the pixels inside the pixel array unit 3.

In Step S2, the correction circuit 11 sets a predetermined pixel unit 31inside the pixel array unit 3 as a target unit to be targeted in orderto calculate a correction coefficient.

In Step S3, the correction circuit 11 calculates a pixel average valueSigAve of pixel signals of four pixels inside the target unit.

In Step S4, the correction circuit 11 calculates the correctioncoefficients a to d of the respective pixels inside the target unit byacquiring the ratio between the pixel average value SigAve and the pixeloutput value of each of the pixels inside the target unit.

In Step S5, the correction circuit 11 determines whether all of thepixel units 31 inside the pixel array unit 3 have been set as the targetunits.

In Step S5, in the case of determining that all of the pixel units 31have not been set as the target units, the processing returns to Step S2and the processing thereafter is repeatedly executed. By this, the pixelunit 31 that has not been set as the target unit is set as the targetunit, and the correction coefficients a to d of the respective pixelsinside the target unit are calculated.

On the other hand, in the case of determining in Step S5 that all of thepixel units 31 have been set as the target units, the processingproceeds to Step S6.

In Step S6, the correction circuit 11 makes the memory 12 store thecalculated correction coefficients a to d of the respective pixel units31 inside the pixel array unit 3, and the correction coefficientcalculation processing ends.

Meanwhile, in the above-described correction coefficient calculationprocessing, provided is the example in which the correction circuit 11also performs adding processing to add the pixel signals of the fourpixels inside the target unit. However, in the case where the pixels 2have the pixel sharing structure illustrated in FIG. 6 , an added signalobtained by adding the pixel signals of the four pixels can be obtainedby FD adding inside the pixel unit 31. Therefore, in the case where thepixels 2 have the pixel sharing structure, the added signal obtained byFD adding inside the pixel unit 31 can be used in calculating the pixelaverage value SigAve.

Flowchart of Correction Coefficient Calculation Processing Using FDAdding

FIG. 11 is a flowchart illustrating the correction coefficientcalculation processing in the case of calculating a correctioncoefficient by using an added signal by FD adding inside the pixel unit31.

According to this processing, first in Step S11, imaging is performedbased on the independent pixel mode in a state that the entire pixelarray unit 3 of the solid-state imaging device 1 is irradiated withuniform light, and the correction circuit 11 of the solid-state imagingdevice 1 obtains and stores pixel signals of all of the pixels insidethe pixel array unit 3

In Step S12, imaging is performed based on the pixel adding mode withuniform light emitted under the same conditions as Step S11, and thecorrection circuit 11 of the solid-state imaging device 1 obtains andstores the added signal for each of the pixel units 31 inside the pixelarray unit 3.

In Step S13, the correction circuit 11 sets a predetermined pixel unit31 inside the pixel array unit 3 as a target unit to be targeted inorder to calculate a correction coefficient.

In Step S14, the correction circuit 11 divides the added signal of thetarget unit by the number of pixels, and calculates the pixel averagevalue SigAve.

The processing from Step S15 to Step S17 is same as the processing fromStep S4 to Step 6 in FIG. 10 , and therefore, the description thereforwill be omitted.

FIG. 12 is a diagram illustrating an exemplary correction table storedin the memory 12 by the correction coefficient calculation processing.

As illustrated in FIG. 12 , the correction coefficients a to d of therespective pixels of the pixel array unit 3 are divided into the pixelA, pixel B, pixel C, and pixel D, and stored in the memory 12 as thecorrection tables.

The number of pixel units 31 in the pixel array unit 3 is X×Y thatincludes X pixel units in an x-direction and Y pixel units in ay-direction. Therefore, pixel A correction coefficients a in the pixelunits 31 inside the pixel array unit 3 are calculated as correctioncoefficients from a₁₁ and a_(XY). The correction coefficient a₁₁ is acorrection coefficient a of the pixel A of the pixel unit 31 positionedat a first pixel unit in the x-direction and a first pixel unit in they-direction inside the pixel array unit 3 when an upper left corner isset as an origin (0, 0). The correction coefficient a₁₂ is a correctioncoefficient a of the pixel A of the pixel unit 31 positioned at thefirst pixel unit in the x-direction and a second pixel unit in they-direction inside the pixel array unit 3. The correction coefficienta₂₁ is a correction coefficient a of the pixel A of the pixel unit 31positioned at a second pixel unit in the x-direction and the first pixelunit in the y-direction inside the pixel array unit 3. The situationsare same in other correction coefficients a.

The pixel B correction coefficients b in the pixel units 31 inside thepixel array unit 3 are also calculated as correction coefficients fromb₁₁ to b_(XY). In the same manner, the pixel C correction coefficients care also calculated as correction coefficients from c₁₁ to c_(XY), andthe pixel D correction coefficients d are also calculated as correctioncoefficients from d₁₁ to d_(XY).

When a mount error of an imaging lens is combined, a sensitivitydifference may have in-plane distribution (tendency to have gradualchange inside the imaging area) relative to an imaging area of the pixelarray unit 3. Such in-plane distribution of the sensitivity differencecan be resolved by holding the correction coefficients as atwo-dimensional table corresponding to the imaging area of the pixelarray unit 3 instead of as a single value relative to the pixel arrayunit 3.

Note that the correction table in FIG. 12 is the example in which thecorrection coefficients are calculated and stored on a one-to-one basisfor the pixels 2 inside the pixel array unit 3. However, the pixel arrayunit 3 may also be divided into regions of, for example, 10×10 or100×100, and one set of correction coefficients a to d may be calculatedand stored for the divided regions as well. In this case, the samecorrection coefficients a to d are applied to the plurality of pixelunits 31 included in one region. In this case also, the correctioncoefficients are held as a two-dimensional table. Therefore, even in theevent of in-plane distribution, a sensitivity difference can becorrected.

Flowchart of Sensitivity Difference Correction Processing

Next, the sensitivity difference correction processing to correct thesensitivity difference by using the correction coefficients stored inthe memory 12 by the correction coefficient calculation processing willbe described with reference to a flowchart in FIG. 13 . The processingis started when imaging is executed after the correction coefficientsare stored in the memory 12, for example.

First, in Step S31, the correction circuit 11 obtains a pixel signal ofeach of pixels imaged in the pixel array unit 3. More specifically, thepixel array unit 3 executes imaging in accordance with predeterminedtiming, and outputs the pixel signal obtained as a result thereof to theAD conversion unit 5. The AD conversion unit 5 converts, to a digitalsignal, the pixel signal of each of the pixels in the pixel array unit 3in accordance with control of the horizontal drive unit 6, and outputsthe digital pixel signal to the correction circuit 11. As a result, thedigital pixel signal of each of the pixels imaged in the pixel arrayunit 3 is supplied to the correction circuit 11.

In Step S32, the correction circuit 11 obtains a correction coefficientstored in the memory 12. Note that this processing can be omitted in thecase where the correction coefficient has been already read in thememory 12.

In Step S33, the correction circuit 11 multiplies a pixel signal of apredetermined pixel supplied from the AD conversion unit 5 by acorrection coefficient (any one of a to d) of the pixel, and calculatesthe pixel signal subjected to sensitivity difference correction. Thecalculated pixel signal subjected to sensitivity difference correctionis output to the output circuit 9.

The processing in Step S33 is executed every time when the pixel signalis supplied from the AD conversion unit 5, and the sensitivitydifference correction processing ends when supply of the pixel signalfrom the AD conversion unit 5 is stopped.

According to the above-described sensitivity difference correctionprocessing, the sensitivity difference is corrected so as to conform tothe pixel output value in the ideal state of having no productionvariation as illustrated in FIG. 7 in any solid-state imaging device 1.Therefore, when the model number of the solid-state imaging device 1 issame, the pixel signal having the same sensitivity can be outputregardless of production time and a production lot, for example. Inother words, sensitivity correction in which a sensitivity differencebetween solid-state imaging devices is suppressed can be performed.

By this, for example, detection accuracy of a phase difference can beprevented from being varied by each chip, and luminance of an image canbe prevented from being varied by each chip when pixel output of thephase difference is utilized for preview and the like at the time offocusing.

According to the present disclosure, the pixel signal having the samesensitivity can be obtained when the model number of the solid-stateimaging device 1 is the same. Therefore, control for a shutter value andimage processing for a captured image are easily performed in an imagingdevice and the like in which the solid-state imaging device 1 isincorporated.

Sensitivity Difference Correction Processing per Wavelength

The factors that may cause variation of the sensitivity difference canbe a wavelength difference of incident light besides productionvariation. As illustrated in FIG. 14 , for example, red light having along wavelength and blue light having a short wavelength have differentcharacteristics in refraction and diffraction as well as differentreaching depths inside a silicon layer.

Therefore, as illustrated in FIG. 15 , the signal processing circuit 8of the solid-state imaging device 1 can provide a correction table sameas FIG. 12 per wavelength (per color) of the light received by the pixel2, such as a red pixel correction table, a green pixel correction table,and a blue pixel correction table. For example, light that passesthrough the red color filter 25 under white light having a specificcolor temperature is the light having a wavelength distribution within ared wavelength band. Therefore, a correction table per wavelength of thelight corresponds to calculation of correction coefficients for thelight having representative wavelength distribution thereof.

Thus, in the case of having the correction table per wavelength of thelight, the pixel array unit 3 is irradiated with uniform light having asingle color temperature in Step S1 of the correction coefficientcalculation processing in FIG. 10 , and a pixel signal of each pixel isobtained. Then, in Step S6, the correction tables are created separatelyfor the red pixel, green pixel, and blue pixel respectively, and storedin the memory 12. By this, the sensitivity difference can be correctedby using the correction coefficients calculated for each of wavelengthbands of red, green, and blue colors. Therefore, highly accuratecorrection can be performed.

Meanwhile, the number of the correction coefficients a to d (M×N) ineach of the red pixel correction table, green pixel correction table,and blue pixel correction table in FIG. 15 is a value corresponding tothe number of the red pixels, green pixels, and blue pixels inside thepixel array unit 3.

Sensitivity Difference Correction Processing in RGBW Array

In the above-described example, description has been provided for thecase where the red, green, or color filters 25 are arranged in the Bayerarray by setting, as a unit, the four pixels having the 2×2 structure ineach of which the microlens 26 is disposed.

However, the color array of the color filters 25 may be another type ofarray, for example, a color array (RGBW array) of red, green, blue, orwhite as illustrated in FIG. 16 by setting, as a unit, the four pixelshaving the 2×2 structure in each of which the microlens 26 is disposed.The white color filter 25 is a filter that transmits light in an entirewavelength band.

In the photodiode PD of the pixel 2 having the white color filter 25(hereinafter also referred to as white pixel), the light of the entirewavelength band including red, green, and blue is incident. Therefore, asensitivity difference is varied by a color temperature of an object.

Therefore, white pixel correction tables for respective colortemperatures, for example, a correction table when the color temperatureis 3000 K, a correction table when the color temperature is 4000 K, anda correction table when the color temperature is 5000 K, are created andstored in the memory 12 as illustrated in FIG. 17 as the white pixelcorrection tables.

In the correction coefficient calculation processing in the case ofhaving the above-described white pixel correction tables for therespective color temperatures, the processing to obtain a pixel signalin the state that the pixel array unit 3 is irradiated with uniformlight having a predetermined color temperature is executed for the whitepixel in the pixel array unit 3 with respect to each of the colortemperatures for which the white pixel correction tables are created.

Further, in the sensitivity difference correction processing of FIG. 13, the correction circuit 11 calculates, from a white pixel to becorrected among pixel signals of respective pixels obtained by imaging,a pixel signal ratio (sensitivity ratio) R/G between the red pixel andthe green pixel, and a pixel signal ratio (sensitivity ratio) B/Gbetween the blue pixel and the green pixel within a local region insidea predetermined range, and estimates a color temperature of the incidentlight based on the result. Further, the correction circuit 11 obtains acorrection coefficient by using the white pixel correction table of theestimated color temperature as the white pixel correction table, andcalculates a pixel signal subjected to sensitivity differencecorrection.

Since the light of the entire wavelength band is incident in the whitepixel, a sensitivity difference depending on the wavelength and thecolor temperature of the object can be easily viewed. However, asdescribed above, highly accurate correction can be performed by usingthe correction table corresponding to the color temperature of theincident light as the white pixel correction table.

In the case where the color array of the color filters 25 is the RGBWarray, the correction table for each of the colors illustrated in FIG.15 can be used for the red pixel, green pixel, and blue pixel other thanthe white pixel. Alternatively, same as the white pixel, the correctiontable per color temperature may be further created for the red pixel,green pixel, and blue pixel as well, and the correction tablecorresponding to the color temperature estimated based on the pixelsignal ratio (sensitivity ratio) using the red pixel, green pixel, andblue pixel may also be used at the time of imaging.

In the case of using the correction table per wavelength or per colortemperature, correction can be performed while resolving the sensitivitydifference varied depending on the color temperature of the object andthe wavelength of the light. Therefore, the sensitivity difference canbe corrected with higher accuracy.

Modified Example of Pixel Unit Arrangement

In the above-described examples, the pixel array unit 3 is formed byregularly arraying the pixel units 31 in a matrix as illustrated inFIGS. 3 and 16 .

However, as illustrated in FIG. 18 , the pixel units 31 may be partlydotted inside the pixel array unit 3, for example.

In a pixel 2 not included in the pixel units 31 inside the pixel arrayunit 3, for example, the color filter 25 and the microlens 61 are formedin each pixel as illustrated in FIG. 18 .

As for the color array of the color filters 25 in the pixel unit 31,red, green, green, and blue are arrayed in the Bayer array in the fourlocal pixel units 31 in the example of FIG. 18 . However, the colorfilters 25 may also be unified to one predetermined color (green, forexample) in all of the pixel units 31 inside the pixel array unit 3.

Other Exemplary Structures of Pixel Unit

FIG. 19 is a diagram illustrating another exemplary structure of thepixel unit 31.

In the above-described examples, the pixel unit 31 is formed of the fourpixels, but in FIG. 19 , the pixel unit 31 is formed of two pixels, andthe microlens 26 is also shared by the two pixels constituting the pixelunit 31.

The color filter 25 of each of the pixels 2 are formed so as to form theBayer array in the unit of one pixel as illustrated in FIG. 19 , forexample.

In the case where the pixel unit 31 is thus formed of the two pixels, aphase difference is detected by, for example, using pixel signals of thetwo pixels in which the same color filters 25 are formed and a shape(curve) of the microlens 26 is symmetric.

FIG. 20 is a diagram illustrating another different example in which thepixel unit 31 is formed of two pixels.

In FIG. 20 , one pixel is formed in a vertically long rectangular shape,and the two pixels constituting the pixel unit 31 forms a square. Themicrolens 26 is arranged in each pixel unit 31, and the color filters 25are formed such that the Bayer array is formed in each pixel units 31.

A phase difference is detected in the pixel unit 31 illustrated in FIG.20 by using pixel signals of the two pixels in which the same colorfilter 25 is formed and the shape (curve) of the microlens 26 issymmetric. For example, the phase difference is detected by using, forexample, the pixel signals of the two pixels horizontally adjacent toeach other inside the pixel unit 31.

FIG. 21 is an explanatory diagram for light intensity of incident lightin the event of positional shift of a microlens 26 in the pixel unit 31illustrated in FIG. 20 .

In the event of positional shift of the microlens 26, as illustrated ina diagram A of FIG. 21 , a center of a dashed-line circle indicating aregion having light intensity of a predetermined value or more isdeviated from the center of the pixel unit 31, and the region inside thedashed-line circle in each of the pixels is different between a pixel Aand pixel B constituting the pixel unit 31. As a result, as illustratedin a diagram B of FIG. 21 , pixel signals (output values) output fromthe respective pixels 2 of the pixel A and the pixel B are different.

The signal processing circuit 8 performs the correction coefficientcalculation processing to calculate a correction coefficient adapted tocorrect a sensitivity difference between the two pixels inside the pixelunit 31 caused by a manufacture error such as positional shift of themicrolens 26 as described above.

In other words, the correction circuit 11 of the signal processingcircuit 8 calculates a pixel average value SigAve of the pixel signalsof the two pixels inside the pixel unit 31 and calculates, as thecorrection coefficients, a ratio between the pixel average value SigAveand the pixel output value of each of the pixels A and B inside thepixel unit 31.

More specifically, the correction circuit 11 calculates a correctioncoefficient a of the pixel A inside the pixel unit 31 based on a ratioSigAve/Sig1 (a =SigAve/Sig1) between the pixel average value SigAve anda pixel output value Sig1 of the pixel A. Further, the correctioncircuit 11 calculates a correction coefficient b of the pixel B insidethe pixel unit 31 based on a ratio SigAve/Sig2 (b=SigAve/Sig2) betweenthe pixel average value SigAve and a pixel output value Sig2 of thepixel B. Further, the calculated correction coefficients a and b in eachof the pixel units 31 are stored in the memory 12.

When imaging is executed, the correction circuit 11 executes thesensitivity difference correction processing to correct the sensitivitydifference by using the correction coefficients stored in the memory 12by the correction coefficient calculation processing.

Except for that the pixel unit 31 is formed of the two pixels instead ofthe four pixels, the details of the correction coefficient calculationprocessing and the sensitivity difference correction processing are sameas the processing described with reference to the flowcharts of FIGS.10, 11 and 13 . Therefore, the description therefor will be omitted.

Further, in the case where the pixel unit 31 is formed of the twopixels, correction tables to be stored in the memory 12 may also be thecorrection table per wavelength or the correction table per colortemperature while setting the color array of the color filters 25 as theRGBW array.

As described above, the pixel unit 31 is at least the unit in which onemicrolens 26 is formed for a plurality of pixels 2, for example, twopixels, four pixel, eight pixels, and so on. However, the boundarybetween the pixel unit 31 is located so as to coincide with theboundaries between the respective pixels 2 each having the photodiodePD.

Exemplary Substrate Configuration of Solid-State Imaging Device

The solid-state imaging device 1 in FIG. 1 can adopt any one ofsubstrate configurations illustrated in diagrams A to C of FIG. 22 .

The diagram A in FIG. 22 illustrates an example in which the solid-stateimaging device 1 is formed on one semiconductor substrate (siliconsubstrate) 81. More specifically, the one semiconductor substrate 81 isformed with a pixel area 91 where a plurality of pixels 2 is arranged ina matrix, a control circuit 92 adapted to control the respective pixels2, and a logic circuit 93 including the signal processing circuit for apixel signal.

The diagram B in FIG. 22 illustrates an example in which the solid-stateimaging device 1 has a stacked structure in which two semiconductorsubstrates 82 and 83 are stacked. More specifically, the pixel area 91and the control circuit 92 are formed on the upper-side semiconductorsubstrate 82, and the logic circuit 93 is formed on the lower-sidesemiconductor substrate 83. The semiconductor substrates 82 and 83 areelectrically connected via a through-via or by metal binding of Cu—Cu,for example.

The diagram C in FIG. 22 also illustrates an example in which thesolid-state imaging device 1 has a stacked structure in which twosemiconductor substrates 84 and 85 are stacked. More specifically, onlythe pixel area 91 is formed on the upper-side semiconductor substrate84, and the control circuit 92 and the logic circuit 93 are formed onthe lower-side semiconductor substrate 85. The semiconductor substrates84 and 85 are electrically connected via a through-via or by metalbinding of Cu—Cu, for example.

2. Second Embodiment Exemplary Schematic Configuration of Solid-StateImaging Device

FIG. 23 is a block diagram illustrating a second embodiment of asolid-state imaging device according to the present disclosure.

In FIG. 23 , a portion corresponding to a first embodiment illustratedin FIG. 1 is denoted by a same reference sign, and a descriptiontherefor will be appropriately omitted.

A solid-state imaging device 1 according to the second embodimentdiffers from a solid-state imaging device 1 according to the firstembodiment illustrated in FIG. 1 in that a memory 12 is not provided ina signal processing circuit 8. In other words, the signal processingcircuit 8 of the solid-state imaging device 1 according to the secondembodiment is formed of only a correction circuit 11.

In the second embodiment, the memory 12 to store a correction table isprovided at a camera module 101 outside the solid-state imaging device1. The correction circuit 11 makes the memory 12 store a correctioncoefficient obtained from correction coefficient calculation processing,and further in the sensitivity difference correction processing, obtainsthe correction coefficient from the memory 12 of the camera module 101and calculates a pixel signal subjected to sensitivity differencecorrection.

3. Third Embodiment Exemplary Schematic Structure of Solid-State ImagingDevice

FIG. 24 is a block diagram illustrating a third embodiment of asolid-state imaging device according to the present disclosure.

In FIG. 24 , a portion corresponding to a first embodiment illustratedin FIG. 1 is denoted by a same reference sign, and a descriptiontherefor will be appropriately omitted.

A solid-state imaging device 1 according to the third embodiment differsfrom a solid-state imaging device 1 according to the first embodimentillustrated in FIG. 1 in that a signal processing circuit 8 is notprovided. In the third embodiment, the signal processing circuit 8 isprovided at a camera module 101 outside the solid-state imaging device1.

In the third embodiment, a pixel signal having a sensitivity differencenot corrected is supplied from an output circuit 9 of the solid-stateimaging device 1 to the signal processing circuit 8 of the camera module101. A correction circuit 11 of the signal processing circuit 8 executescorrection coefficient calculation processing and makes a memory 12store a correction coefficient to correct the sensitivity difference.Further, the correction circuit 11 executes sensitivity differencecorrection processing in the case where a pixel signal of a capturedimage is supplied from the solid-state imaging device 1. Morespecifically, the correction circuit 11 obtains the correctioncoefficient from the memory 12 of the camera module 101, and appliessensitivity difference correction to the pixel signal from thesolid-state imaging device 1, and outputs the pixel signal subjected tosensitivity difference correction to a circuit in a following stage.

As described above, both or one of the correction circuit 11 and thememory 12 can be provided outside the solid-state imaging device 1.

4. Exemplary Application to Electronic Apparatus

The above-described solid-state imaging device 1 is applicable to animaging device such as a digital still camera and a digital videocamera, a mobile phone having an imaging function, or various kinds ofelectronic apparatuses such as an audio player having an imagingfunction.

FIG. 25 is a block diagram illustrating an exemplary configuration of animaging device as an electronic apparatus according to an embodiment ofthe present disclosure.

An imaging device 201 illustrated in FIG. 25 includes an optical system202, a shutter device 203, a solid-state imaging device 204, a controlcircuit 205, a signal processing circuit 206, a monitor 207, and amemory 208, and can image a still image and a moving image.

The optical system 202 is formed of one or a plurality of imaginglenses, and guides light (incident light) from an object to thesolid-state imaging device 204, and forms an image on a light receivingsurface of the solid-state imaging device 204.

The shutter device 203 is disposed between the optical system 202 andthe solid-state imaging device 204, and controls a light emitting periodand a light shielding period relative the solid-state imaging device 204in accordance with control of the control circuit 205.

The solid-state imaging device 204 is formed of a solid-state imagingdevice 1 described above. The solid-state imaging device 204 accumulatessignal charge for a predetermined period in accordance with the lightwith which the image is formed on the light receiving surface via theoptical system 202 and the shutter device 203.

The signal charge accumulated in the solid-state imaging device 204 istransmitted in accordance with a drive signal (timing signal) suppliedfrom the control circuit 205. The solid-state imaging device 204 may beformed as one chip by itself, and may be formed as a part of a cameramodule packaged with the optical system 202, the signal processingcircuit 206, and the like.

The control circuit 205 outputs a drive signal to control transmittingoperation of the solid-state imaging device 204 and shutter operation ofthe shutter device 203, and drives the solid-state imaging device 204and the shutter device 203.

The signal processing circuit 206 applies various kinds of signalprocessing to a pixel signal output from the solid-state imaging device204. An image (image data) obtained from the signal processing appliedby the signal processing circuit 206 is supplied to and displayed on amonitor 207, or supplied to and stored (recorded) in the memory 208.

As described above, by using the solid-state imaging device 1 accordingto each of the above-described embodiments as the solid-state imagingdevice 204, it is possible to perform sensitivity correction in which asensitivity difference between the solid-state imaging devices issuppressed. Therefore, high image quality can be also achieved for acaptured image in the imaging device 201 such as a video camera, digitalstill camera, and also a camera module used in a mobile device like amobile phone.

The embodiments of the present disclosure are not limited to theabove-described embodiments, and various kinds of modifications can bemade within a range not departing from a gist of the present disclosure.

In the above-described embodiment, described is the solid-state imagingdevice in which the first conductive type is set as a p-type, the secondconductive type is set as an n-type, and electrons are deemed as thesignal charge. However, the present disclosure is also applicable to asolid-state imaging device in which an electron hole is deemed as thesignal charge. In other words, each of the above-described semiconductorregions can be formed of a semiconductor region having a reverseconductive type by setting the first conductive type as the n-type andthe second conductive type as the p-type.

Further, application of the present disclosure is not limited to asolid-state imaging device that detects distribution of incident lightamounts of visible light and captures the distribution as an image. Thepresent disclosure is applicable to a solid-state imaging device thatcaptures distribution of indecent light amounts of infrared, X-ray,particles, or the like as an image, and in a broad sense, applicable toa general solid-state imaging device (physical amount distributiondetection device) such as a fingerprint detection sensor that detectsdistribution of other physical amounts like pressure and electrostaticcapacitance and that captures the distribution as an image.

An embodiment optionally combining all or part of the above-describedembodiments can be adopted.

Note that the effects recited in the present specification are merelyexamples and not limited thereto, and effects other than those recitedin the present specification may be provided as well.

Further, the present technology can also have the followingconfigurations.

(1)

A solid-state imaging device includes:

a pixel unit in which one microlens is formed for a plurality of pixelsin a manner such that a boundary of the microlens coincides withboundaries of the pixels; and

a correction circuit that adapted to correct a sensitivity differencebetween pixels inside the pixel unit based on a correction coefficient.

(2)

The solid-state imaging device according to above (1), wherein thecorrection coefficient is calculated based on an added signal obtainedby adding pixel signals of the respective pixels of the pixel unit.

(3)

The solid-state imaging device according to above (2), wherein the pixelunit includes an adding unit configured to generate the added signal.

(4)

The solid-state imaging device according to above (3), wherein theadding unit is an FD shared by respective pixels of the pixel unit.

(5)

The solid-state imaging device according to any one of above (2) to (4),wherein the correction coefficient is calculated based on a pixelaverage value obtained by dividing the added signal by the number ofpixels of the pixel unit.

(6)

The solid-state imaging device according to above (5), wherein thecorrection coefficient is calculated by a ratio between the pixelaverage value and a pixel signal of each of the pixels of the pixelunit.

(7)

The solid-state imaging device according to above (2), wherein thecorrection circuit also performs adding processing in which the addedsignal is calculated by adding pixel signals of respective pixels of thepixel unit.

(8)

The solid-state imaging device according to any one of above (1) to (7),further including a memory adapted to store the correction coefficient,wherein the correction circuit performs correction based on thecorrection coefficient obtained from the memory.

(9)

The solid-state imaging device according to any one of above (1) to (8),wherein

a plurality of the pixel units is arranged inside a pixel array unit inwhich the pixels are two-dimensionally arrayed in a matrix, and

the correction coefficient is provided for each of pixels constitutingthe pixel unit.

(10)

The solid-state imaging device according to any one of above (1) to (9),wherein

a plurality of the pixel units is arranged inside a pixel array unit inwhich the pixels are two-dimensionally arrayed in a matrix, and

the correction coefficient is provided for each of regions obtained bydividing the pixel array unit into predetermined number.

(11)

The solid-state imaging device according to any one of above (1) to(10), wherein the correction coefficient is provided per wavelength oflight received by the pixel.

(12)

The solid-state imaging device according to any one of above (1) to(11), wherein the correction coefficient is provided per colortemperature of light received by the pixel.

(13)

The solid-state imaging device according to above (12), wherein thecorrection circuit uses a pixel signal of another pixel to estimate acolor temperature of light received by the pixel, and performscorrection based on the correction coefficient corresponding to theestimated color temperature.

(14)

The solid-state imaging device according to above (13), wherein thepixel from which a color temperature of light is estimated is a whitepixel formed with a white color filter.

(15)

The solid-state imaging device according to any one of above (1) to(14), wherein the solid-state imaging device is a back-illuminationtype.

(16)

The solid-state imaging device according to any one of above (1) to(15), having a stacked structure in which a plurality of semiconductorsubstrates is stacked.

(17)

A signal processing method in a solid-state imaging device, wherein thesolid-state imaging device includes a pixel unit in which one microlensis formed for a plurality of pixels in a manner such that a boundary ofthe microlens coincides with boundaries of the pixels, and a correctioncircuit of the solid-state imaging device corrects a sensitivitydifference between pixels inside the pixel unit based on a correctioncoefficient.

(18)

An electronic apparatus provided with a solid-state imaging device thatincludes:

a pixel unit in which one microlens is formed for a plurality of pixelsin a manner such that a boundary of the microlens coincides withboundaries of the pixels; and

a correction circuit adapted to correct a sensitivity difference betweenpixels inside the pixel unit based on a correction coefficient.

REFERENCE SIGNS LIST

-   1 Solid-state imaging device-   2 Pixel-   3 Pixel array unit-   8 Signal processing circuit-   11 Correction circuit-   12 Memory-   31 Pixel unit-   25 Color filter-   26 Microlens-   PD Photodiode-   81 to 85 Semiconductor substrate-   201 Imaging device-   204 Solid-state imaging device

The invention claimed is:
 1. A solid-state imaging device comprising: apixel unit in which a microlens is formed for a plurality of pixels; anda correction circuit configured to correct a sensitivity differencebetween pixels inside the pixel unit based on a correction coefficient,wherein the correction coefficient is calculated based on an addedsignal obtained by adding pixel signals of respective pixels of thepixel unit, wherein the correction coefficient is calculated based on apixel average value obtained by dividing the added signal by a number ofpixels of the pixel unit, and wherein the correction coefficient iscalculated by a ratio between the pixel average value and a pixel signalof each pixel of the pixel unit.
 2. The solid-state imaging deviceaccording to claim 1, wherein the pixel unit includes an adding unitconfigured to generate the added signal.
 3. The solid-state imagingdevice according to claim 2, wherein the adding unit is a floatingdiffusion (FD) shared by respective pixels of the pixel unit.
 4. Thesolid-state imaging device according to claim 1, wherein the correctioncircuit also performs adding processing in which the added signal iscalculated by adding the pixel signals of the respective pixels of thepixel unit.
 5. The solid-state imaging device according to claim 1,further including: a memory configured to store the correctioncoefficient, wherein the correction circuit performs correction based onthe correction coefficient obtained from the memory.
 6. The solid-stateimaging device according to claim 1, wherein a plurality of pixel unitsare arranged inside a pixel array unit in which pixels aretwo-dimensionally arrayed in a matrix, and wherein the correctioncoefficient is provided for each pixel constituting the pixel unit. 7.The solid-state imaging device according to claim 1, wherein a pluralityof pixel units are arranged inside a pixel array unit in which pixelsare two-dimensionally arrayed in a matrix, and the correctioncoefficient is provided for each region obtained by dividing the pixelarray unit into a predetermined number.
 8. The solid-state imagingdevice according to claim 1, wherein the correction coefficient isprovided per wavelength of light received by a pixel.
 9. The solid-stateimaging device according to claim 1, wherein the correction coefficientis provided per color temperature of light received by a pixel.
 10. Thesolid-state imaging device according to claim 9, wherein the correctioncircuit uses a pixel signal of another pixel to estimate a colortemperature of light received by a pixel, and performs correction basedon the correction coefficient corresponding to the estimated colortemperature.
 11. The solid-state imaging device according to claim 10,wherein the pixel for which the color temperature of light is estimatedis a white pixel formed with a white color filter.
 12. The solid-stateimaging device according to claim 1, wherein the solid-state imagingdevice is a back-illumination type.
 13. The solid-state imaging deviceaccording to claim 1, wherein the solid-state imaging device has astacked structure in which a plurality of semiconductor substrates arestacked.
 14. A signal processing method in a solid-state imaging device,wherein the solid-state imaging device includes: a pixel unit in which amicrolens is formed for a plurality of pixels; and a correction circuitof the solid-state imaging device configured to correct a sensitivitydifference between pixels inside the pixel unit based on a correctioncoefficient, wherein the correction coefficient is calculated based onan added signal obtained by adding pixel signals of respective pixels ofthe pixel unit, wherein the correction coefficient is calculated basedon a pixel average value obtained by dividing the added signal by anumber of pixels of the pixel unit, and wherein the correctioncoefficient is calculated by a ratio between the pixel average value anda pixel signal of each pixel of the pixel unit.
 15. An electronicapparatus provided with a solid-state imaging device that includes: apixel unit in which a microlens is formed for a plurality of pixels; anda correction circuit configured to correct a sensitivity differencebetween pixels inside the pixel unit based on a correction coefficient,wherein the correction coefficient is calculated based on an addedsignal obtained by adding pixel signals of respective pixels of thepixel unit, wherein the correction coefficient is calculated based on apixel average value obtained by dividing the added signal by a number ofpixels of the pixel unit, and wherein the correction coefficient iscalculated by a ratio between the pixel average value and a pixel signalof each pixel of the pixel unit.